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dennisinaz
07-18-2011, 01:12 AM
On a rifle that will typically be used with ammo made with 7/8-14 threaded dies and often full- length resized, how much clearance do you really need on the neck. Should a bullet slide easily into the fired case or is a very slight friction fit acceptable?

On this particular rifle, I , theoretically, have .003 total clearance. I can stick a bullet back into a fired case, but it will not fall through.

nhkuehl
07-18-2011, 09:34 AM
That's about the same clearance that I have with Lapua brass in my 6mm BR with a .272 no-turn neck. A bullet will slip into a fired case neck, but stops at the donut at the neck-shoulder junction. - nhk

Dennis Sorensen
07-18-2011, 11:06 AM
Brass springs back a bit after firing. Often a bullet will not 'clear' a firing neck if the chamber tolerances are close. That is why you should know what the chamber neck diameter is and measure loaded rounds to determine clearance.

dennisinaz
07-19-2011, 02:10 AM
I have measured the loaded rounds- .294, the chamber is supposed to be .297 if Kiff hit his mark. That makes .003" total clearance or .0015 per side. I haven't had a "no-turn" neck quite this tight, just wondering if I am really going to get away with it or not.

Dennis Sorensen
07-19-2011, 10:49 AM
If you can obtain a short piece of barrel and have the reamer run in to cut a throat and neck... you could use it to check your reloads... but the minimum clearance is okay as long as you don't have an out of spec thick brass show up.

passion4shootin
07-19-2011, 04:00 PM
If you can obtain a short piece of barrel and have the reamer run in to cut a throat and neck... you could use it to check your reloads... but the minimum clearance is okay as long as you don't have an out of spec thick brass show up.

Hey, thats a good idea. Just cut as far as the throat and neck to act as a clearance checker or case gauge.

Thanks for that good tip Dennis!

alinwa
07-22-2011, 03:37 AM
that is an especially nice gizzie design :) lets you see the neck length clearance or 'gap space."

chino69
07-22-2011, 10:32 AM
I have a couple of those but none are milled to show the new length clearance or land interface. It would be a simple matter to have them modified.

dennisinaz
07-22-2011, 10:33 AM
I have one of those for my 6.5-284 (without the window in it) but that still doesn't tell me if I have enough clearance- at .003 under it will certainly fit, just wondering if it will give a clean release or not. I guess I will shoot a couple of groups with unturned brass and a couple with about .0008-.001 turned off and see if the SD and velocities change at all.

I don't have and barrel left to make one on this rifle- I could use another piece of barrel but it wouldn't really tell me anything about my throat as the dimensions could be completely different!

Dennis Sorensen
07-22-2011, 11:02 AM
Clearance is clearance.. if there is clearance the bullet will release... 3 thou is fine. 1 thou is fine... the case neck/bullet are not being crushed/compressed by the chamber... if there is a lot of clearance the bullet will release and the neck of the brass will expand beyond it's elastic abilities and be larger.

If there isn't clearance the round will have to be forced into the neck area, the bullet will release but pressures will be higher. I don't think you have a problem if you have accurately measured the clearance.

Greg Walley
07-22-2011, 11:06 AM
Your rifle will shoot better with at least .002” total clearance. As a general rule, the bullets should easily slide through the necks of fired cases with little or no resistance.

Greg Walley
Kelbly’s Inc.

jackie schmidt
07-22-2011, 05:02 PM
I agree with Greg. That is a pretty good test to see if you have it right.

If it will not, you need to make sure that you do indeed have the correct neck diameter. For instance, just because a reamer is stamped .269 does not mean it will cut a .269 neck. If your loaded rounds measure .267, and a bullet will not slip into a fired vase, there is a good chance your reamer is a tad undersize........jackie

Al Nyhus
07-22-2011, 05:37 PM
Have several double-gizmos here....different chambers on each end:

http://img.photobucket.com/albums/v467/tenxal/g1-1.jpg

http://img.photobucket.com/albums/v467/tenxal/g2.jpg

http://img.photobucket.com/albums/v467/tenxal/g3.jpg

don carter
07-24-2011, 03:44 PM
Does anyone make bushings for .30 cal. in .ooo5 increments ? Thanks Don

Wilbur
07-24-2011, 06:10 PM
6PPC fired necks will (for several firings) almost always measure .001 less then the chamber neck diameter. I wanted to say always but couldn't.

I had a seater die that I cussed for a whole season. The neck diameter in the seater wasn't much (if any) over the .261 neck of my rifle and some rounds would stick while others wouldn't let the bullet seat. I cussed it up until the moment I realized that it was trying to tell me something and I wasn't listening. Sure, there are many methods to prevent loading up a negative clearance round but such a seater is a great "last chance". How many times has someone said "here, try these bullets"?